Gangliosides play critical roles in cell-cell interactions as differentiation markers and receptors or modifiers of receptors for toxins, hormones and other factors. Malignant transformation frequently results in changes in ganglioside pattern and the importance of gangliosides for detection and treatment of cancer has recently been established. However, gangliosides are rarely highly immunogenic, thwarting attempts at active immunization or production of monoclonal antibodies in many cases and resulting in production of exclusively IgM antibodies in others. We have shown recently that IgM antibodies can be induced consistently after immunization with selected vaccines in man and the mouse (and IgM monoclonal antibodies), but that IgG antibodies or T cell immunity are not induced. This pattern of immunogenicity is strongly suggestive of the split tolerance seen against other autoimmunogenic differentiation antigens. Covalent attachment of poorly immunogenic or tolerated antigens to strongly immunogenic proteins has been the most potent method for replacing T cell help and inducing IgG antibodies to these antigens. Using GM2 as a model for all gangliosides, we propose to develop and test different methods of covalently attaching GM2 to two potent protein antigens, BSA and KLH. The relative immunogenicity of the different complexes will be determined in mice and methods to further increase their immunogenicity in various types of vaccines explored. The immune response in vaccinated mice will be dissected in vitro using in vitro methods and assays to better understand the host response to gangliosides and methods to increase it. Approaches shown to be optimal for GM2 will be applied to GD2, GD3, GM3 and other gangliosides. Our previous studies on the induction of IgM antibodies against gangliosides in the mouse have been rapidly translated into adjuvant trials in melanoma patients and the production of human monoclonal antibodies. We anticipate a similar pattern with regard to these studies on the induction of IgG antibodies.